Bach's hand was comparatively small; the movement of his fingers was hardly perceptible, extending only to the first joints. His hand preserved its rounded shape even in the most difficult passages, Forkel tells us; the fingers were raised very little above the keyboard, hardly more than in a trill; as soon as a finger was no longer needed, he took pains to replace it in its normal position.... "The other parts of his body took no part in the performance, contrary to the habit of many people whose hands are incapable of sufficient agility." To-day we no longer play the harpsichord; and the pianoforte, which has happily replaced it, makes demands never dreamed of in those days. As to the character of organ touch, no change has taken place in two centuries. Possibly at the time of Bach the keys of the pedals were slightly different from those of our day; undoubtedly in his youth he made much less use of the heel than of the toe, since the pedal-keys were extremely short. But he soon recognized the necessity of perfecting the bass keyboard of the organ both by extending its compass and by lengthening the pedal-keys to their present dimensions. He played with the body inclined slightly forward, and motionless; with an admirable sense of rhythm, with an absolutely perfect polyphonic ensemble, with extraordinary clearness, avoiding extremely rapid _tempi_; in short, master of himself, and, so to speak, of the beat, producing an effect of incomparable grandeur. His contemporaries speak enthusiastically of his exquisite taste in the combination of registers, and of his manner of treating them, at once so unexpected and original. Nothing could escape him which was related to his art, adds Forkel. He observed with the most minute attention the acoustic properties of the room where he was to play. On his visit to Berlin in 1747, he was conducted to the auditorium of the new opera house. He recognized at a glance the advantages and defects of this monumental edifice, in its relation to music. He was shown the _grand foyer_ adjacent. Standing in the mezzanine gallery, he glanced up toward the ceiling and remarked immediately, without giving himself the trouble of further examination, that in it the architect had constructed "a work of great merit," perhaps unawares. The _foyer_ was in the form of a parallelogram; if a person standing in a corner of it, face toward the wall, spoke a few words, another person standing in the same position in the corner diagonally opposite could distinctly hear them, while the public, scattered here and there through the hall, would be unable to catch anything of this dialogue.